1. Field of the Invention
The invention relates to a charging control method of a rechargeable battery, and more particularly, to a charging control method capable of prolonging the battery life.
2. Description of the Prior Art
Considering the convenience of using an electronic system and the capacity requirement of the power supply, most electronic systems adapt rechargeable battery as the source of its power supply, in which the batteries using lithium polymer as core substance are regarded as the most mature products with high capacity density specification. The rechargeable battery is primarily charged by a power supply unit or via an AC adapter from an electronic system where the rechargeable battery is installed. When the electronic system such as a laptop computer is in use, with the AC adapter connected, the electronic system usually consumes power from the power source via the AC adapter instead of from the rechargeable battery. Once the power from the AC adapter is disconnected from the electronic system, the rechargeable battery provides power for the electronic system until the AC adapter with power is reconnected to both provide power for the electronic system and charge the rechargeable battery all the way when the rechargeable battery reaches the full charge capacity (FCC). Such repetitive change between fully charged state and not fully charged state is very common for the rechargeable battery. One nature of the rechargeable battery should be taken care of: the life of a rechargeable battery may be damaged when the rechargeable battery is connected to the power supply unit and stays constantly at the 100% fully charged state for a quite a long time.
On the other hand, some regularity may exist according to how a user uses the electronic system. For example, the user may plug an AC adapter to a laptop computer but not use it within a certain period of time for each day. According to the charging design of the prior art, the rechargeable battery of the laptop computer may be charged and maintained at the FCC for at least a couple of hours in the time interval every day, let's say the couple of hours during the night time. It apparently causes unrecoverable damage to the rechargeable battery if the charging scheme of the prior art is adapted.